OF THE PROTOZOA, CILIATA. 367 



a transverse ring of very fine vibratile cilia may be perceived at a short 

 distance from its summit." 



This rapidly- mo\dng embryo was followed in its course, under " the mi- 

 croscope, and was seen to traverse " the di^op of water from one side to the 

 other, in divers straight and imdulating lines, as quick as Hghtning. Upon 

 meeting a mass of mucus on the edge of the drop, it bounced back again, re- 

 peating the manoeuvre on each occasion of the same kind ; sometimes, though 

 more rarely, the movement was circular, around the margin of the drop. 



'' Judging from what I had noticed in the division of the PodopJiryce, I 

 expected that the movement would not be of long duration. But after a 

 continuous observation, for fully five hours, of the active motions of the tiny 

 brilhant point, a determination of blood to the head obliged me to desist. 



" A fresh drop of the infusion, in which two embryos were in active mo- 

 tion, was observed at intervals of a quarter of an hour. At the end of five 

 hours, the rapidity of the movement was notably diminished — it became tre- 

 mulous, and then, perhaps, for a time, as rapid and energetic as before. I 

 now placed the object under the compound microscope, and continued my 

 observation of the indefatigable embr^'o for another quarter of an hour ; the 

 embryo became stationaiy. I waited with drawn breath what would come 

 next : its form from oval became spherical ; at the border appeared short, 

 thick, equidistant rays, which, after a wliile, were developed into elongated, 

 capitate tentacles ; the contractile space was visible ; and I could no longer 

 doubt as to the Acineta-ndituxe of the creature (XXIII. 42, 43). This obser- 

 vation was twice repeated. 



*' It can, therefore, no longer be doubted that from the Acineta-emhvjo, 

 after a prolonged motile stage, another Acineta is formed. My observations 

 do not, of course, show that it is impossible that the motile Acineta-emhvyo 

 should be transformed into a VorticeUa, and a VorticeJla-Qj^tmiQ an Acmeta ; 

 but the field of possibilities is very wide ; everything is possible if it only be 

 founded on facts. I behove, therefore, that it may justly be concluded that 

 Stein's Acineta doctrine, as concerns VorticeUa microstoma (Ehr.), must be 

 regarded as hypotheticcd , and not based upon facts." 



Lachmann and Claparede have jointly examined into the facts and appear- 

 ances upon which Stein's hypothesis is based, and have presented an abstract 

 of their views, which are entirely adverse to it, in the AnnaJes des Sciences 

 Naturelles, 1858, in anticipation of the publication of their essay, to which 

 the French Academy awarded the first prize for original researches into 

 the development of Infusoria. They state that they have witnessed the 

 development of embryos in many other Acinetina besides those recognized 

 by Stein : that the embryos of difi'erent species vary ; that the tentacles 

 of Acinetina are suctorial and active in seizing food, which is absorbed 

 with avidity into the interior ; and that the internal organization of those 

 animalcules is in all probability more elaborate than Stein supposed. 



The appearance of the joint essay on the development of the Infusoria, by 

 the gentlemen mentioned, as well as of that by Lieberkiihn, which shared in 

 the prize ofi'ered, will be anticipated with much eagerness and pleasure by 

 all naturahsts who feel how obscure and confused is the present state of in- 

 formation on the subject. 



At the present time, we may say that Stein's hypothesis of the transform- 

 ation of Ciliated Protozoa (or, more strictly, of the VorticelUna and Ophry- 

 dina, to which alone it has been sought to refer it by observation) remains 

 unproven ; yet doubtless it is a step in the right direction to arrive at a know- 

 ledge of the true generative process of these animalcules, and has ah^eady proved 

 the development of ciliated embryos in Aciyietina and in various Ciliata. 



